Organic phosphines, their phosphonium halides and methods for preparation thereof



Patented Aug. 24, 1954 UNITED STATES PATENT OFFICE ORGANIC PHOSPHINES,THEIR PHOSPHO- NIUM HALIDES AND METHODS FOR PREP- ARATION THEREOF AlfredL. Oppegard, Wilmington Manor, Del., assignor to E. I. du Pont deNemours and Company, Wilmington, Del., a corporation of Delaware NDrawing. Application April 20, 1951, Serial No. 222,155

chemical compound and a variety of methods have been proposed forpreparing them. However,. the best of the hitherto known methods involvethe use of relatively expensive intermediates and, hence, have not beendesirable for commercial development.

It is an object of this invention to provide a novel process for thepreparation of organic phosphines and. their phosphonium salts. Afurther object is to provide a novel catalytic process for thepreparation of organic phosphines and their phosphonium salts. A stillfurther object is to provide novel organic phosphines, addition productsand phosphonium salts thereof. Other objects will appear hereinafter.

The objects of this invention are accomplished by the following processwhich comprises heating a mixture of hydrocarbon havin at least oneolefinic double bond, white phosphorus and hydrogen at a temperatureabove 200 C. and under a pressure of 700 to 3000 atmospheres. It has nowbeen found that organic phosphines can be prepared by the thermaladdition of phosphorus and hydrogen to the double bond of an olefiniccompound. The reaction can also be carried out in the presence of acatalyst, e. g., a halogen or a halogen compound. The use of suchcatalysts permits the reaction to be carried out at lower temperaturesthan when no catalyst is employed. Tricyclohexylphosphine, itsphosphonium salts, and the carbon disulfide adduct oftricyclohexylphosphine are a novel class of compounds and they form apart of this invention.

A preferred method for carrying out the process of this inventioninvolves heating a mixture of from 3 to 6 moles of a hydrocarbon hav- 16Claims. (Cl. 260-607) used it is convenient to use an inert organicsolvent such as a hydrocarbon or ether. The reaction is continued untila substantial amount of the desired phosphine is obtained. Usuallyreaction times of from 10 to 20 hours are sufficient.

I Reaction times of less than 10 hours do not give ing at least oneolefinic double bond, e. g., ethylene, butadiene or cyclohexene, with 1mole of white phosphorus under a hydrogen pressure of 800 to 1000atmospheres at a temperature of 250 to 400 C. Optionally, the reactioncan be carried out in the presence of a catalyst, e. g., a halogen suchas iodine or a halogen compound such as methyl iodide or phosphorustribromide. When a catalyst is used, the preferred reaction temperatureis 250 to 350 0., while in the absence of a catalyst slightly highertemperatures, e. g., 300 to 400 C., are preferred. The reaction takesplace in the absence of a solvent. How'- ever, in some cases when lowboiling olefins are complete reaction. The reaction can be consideredcomplete when hydrogen is no longer absorbed by the reaction mixture, 1.e., when there is no further drop in pressure in the system.

The organic phosphines obtained in this process can be isolated from thereaction mixture by conventional methods, e. g., by fractionaldistillation. They can also be isolated by reaction of the crudephosphines with carbon disulfide followed by recrystallization of theresulting tertiary phosphine-carbon disulfide complex. When the reactionis carried out in the presence of a catalyst such as methyl iodide orcyclohexyl iodide, some of the phosphonium salts are formed. Forexample, in the reaction of ethylene in the presence of methyl iodide ascatalyst, tetraethylphosphonium iodide is formed, and in the reaction ofcyclohexene with cyclohexyl iodide as catalyst, tricyclohexylphosphinehydroiodide is formed. These phosphonium salts are conveniently isolatedby crystallization.

The ethylenically unsaturated compounds, the white phosphorus, and thehydrogen used in the process of this invention can be the ordinarygrades of materials commercially available.

The invention is further illustrated by the following examples in whichthe proportions of ingredients are expressed in parts by weight, unlessotherwise noted.

Example I and heating are started. The reaction is conducted at atemperature of 250 C. at 800 atmospheres pressure for 4 hours and at 250C. and 950-980 atmospheres pressure for 11 hours. The pressure ismaintained at these values by intermittent repressuring with hydrogen asneeded. The total pressure drop during the reaction is atmospheres.After the total reaction time 3 of 15 hours the reactor is allowed tocool to room temperature and the internal pressure reduced toatmospheric by venting the gases to the atmosphere. The reaction productconsists of 42 parts of a colorless liquid and 42 parts of a wet graysolid. Distillation of the liquid at atmospheric pressure under nitrogenyields 33 parts of cyclohexane and 4 parts of a liquid residue. Thisresidue is diluted with diethyl ether and treated with carbon disulfide.There is obtained 2 parts of triethylphosphine-carbon disulfide additioncompound, (C2H5)3P.CS2, melting at 108-110 C.

Analysis calculated for C'IHI5PS2Z C, 43.30%; H, 7.74%; P, 16.00%; S,33.00%

Found:

The gray solid portion of the reaction product is washed withcyclohexane and extracted with hot ethanol. All of this solid but onepart of a black residue dissolved in the alcohol. Upon cooling, thefiltered alcoholic solution deposits white crystals oftetraethylphosphonium iodide, amounting to 15 parts. This material, onrecrystallization from ethanol, has a melting point of 280-284 C.

Analysis calculated for CsHzoPIt P, 11.30%; I, 46.40% Found:

Triethylphosphine can be obtained from tetraethyphosphonium iodide bythermal decomposition followed by distillation. Triethylphosphine boilsat 128 0.

Example II A pressure reactor of the type used in Example I is chargedwith 10.3 parts (0.33 mole) of white phosphorus, 28 parts (1 mole) ofethylene and 50 parts of cyclohexane and pressured with hydrogen as inExample I. The reactor is agitated and heated at 300 C. under 1000atmospheres pressure for 15 hours. During this time the reactor isrepressured with hydrogen as necessary to maintain the 1000 atmospherespressure. The total pressure drop during the reaction amounts to 150atmospheres. The reaction product is a liquid amounting to 60 parts. Ondistillation there is removed 37.5 parts of cyclohexane leaving aresidue of 15.5 parts. This residue is fractionally distilled through amicro-Podbielniak still. The following fractions are obtained.

Fraction Boiling Point E Amount, 1111.

Residue";

4 and forms a picrate, M. P. Ill-113 0. Fraction 5 has the followingelemental analysis:

C, 63.21%; H, 12.27%; P, 24.43% 62.86% 12.01% 24.57%

These analytical data indicate that higher phosphines are formed inaddition to triethylphosphine. The residue is a high boiling liquid plussome solid.

Example III A pressure reactor of the type used in the precedingexamples is charged with 10.3 parts (0.33 mole) of white phosphorus and54 parts (1 mole) of butadiene in 35 parts of diethyl ether. The reactoris pressured with hydrogen as in the preceding examples and the reactionmixture heated and agitated at 300 C. for 15 hours under 1000atmospheres hydrogen pressure. The total pressure drop during thereaction is atmospheres. The reaction product consists of 72 parts of aclear liquid and 4 parts of a pasty red solid. Ether is removed from theliquid product and the residue is distilled under reduced pressure.There are obtained a volatile fraction boiling at 78 C./165 mm. to C./7mm. amounting to 13 parts, and 20 parts of a clear, colorless, veryviscous residue containing 10.23% phosphorus. 75.90% carbon and 11.17%hydrogen. The residue is soluble in ether and gives a red color withcarbon disulfide, and apparently consists of low molecular weightpolymers of outadicne containing phosphorus. The red color obtained withcarbon disulfide indicates the presence of tertiary phosphines.

Example IV A pressure reactor of the type used in the preceding examplesis charged with 164 parts (2 moles) of cyclohexene, 21 parts (0.1 mole)of cyclohexyl iodide and 20.6 parts (0.66 mole) of white phosphorus.This mixture is heated at 250 C. for 15 hours under 1000 atmosphereshydrogen pressure. The system is represented with hydrogenintermittently to maintain the pressure at 1000 atmospheres. A totalpressure drop of 450 atmospheres occurs during the reaction. Thereaction mixture consists of 121.3 parts of a cloudy, reddish liquid and63 parts of damp, red phosphorus. On distillation of the liquid fractionthere are recovered 48 parts of cyclohexane, and traces of phosphine aredetected in the residue of the distillation. The red solid portion ofthe reaction mixture is washed with benzene and then extracted with hotacetone followed by hot ethanol. From the acetone extract there isisolated 4 parts of white crystals of tetracyclohexylphosphonium iodide.After recrystallization from methanol and from ethyl acetate-ethanol thephosphonium iodide has a melting point higher than 310 C.

Analysis calculated for CzrHaPI:

C, 58.80%; H, 9.00%; P, 6.33%; I, 25.90% Found:

Crystals of tricyclohexylphosphine hydroiodide, amounting to 5 parts,are obtained from the ethanol extract. After recrystallization thesecrystals melt at ISO-183 C.

Analysis calculated for C1am4PI:

P, 7.60%; I, 31.55% Found:

Tricyclohexylphosphine is isolated by treating tricyclohexylphosphinehydroiodide with sodium hydroxide to liberate the free base. Thetrycyclohexylphosphine is identified by dissolving it in diethyl ether,and treating the dry ether solution with carbon disulfide. The resultingred addition product of carbondisulfide and tricyclohexylphosphine meltsat 115-117 C. A sample of tricyclohexylphosphine-carbon disulfideadduct, obtained from tricyclohexylphosphine prepared by reaction ofphenylmagnesium bromide with phosphorus trichloride, melts at 112115 C.,and a mixed melting point of the two samples is 115- 117 C. Thetricyclohexylphosphine melts at 74- 76" C. It forms a sulfide, M. P.172-175" C. and tricyclohexylmethylphosphonium iodide, M. P. 182184 C.

Example V A pressure reactor of the type used in the preceding examplesis charged with 164 parts (2 moles) of cyclohexene, 14.2 parts (0.1mole) of methyl iodide, and 20.6 parts (0.66 mole) of white phosphorus.This mixture is heated at 250 C. for 15 hours'under 1000 atmosphereshydrogen pressure. Three such runs are made, each run being repressuredwith hydrogen intermittently to maintain the pressure at 1000atmospheres. A total drop of 1285 atmospheres occurs in the threereactions. The products are combined and consist of 194 parts of darkred solid and 347.5 parts of liquid. The liquid is distilled to obtain204.4 parts of cyclohexane and 90 parts of liquid residue. This residueis fractionally distilled through a Podbielniak still. The followingcompounds are obtained.

1. Cyclohexylphosphine, B. P. 97 C. 160 mm., 20 parts.

Analysis calculated for Cs-HiaP: C, 62.00%, H, 11.20%

P, 26.75% Found:

C, 62.17%; H, 11.34% 62.02% 11.44% P, 26.47% 26.40%

The structure is proved by oxidation of a concentrated hydrochloric acidsolution of the product with nitric acid to obtain cyclohexanephosphonicacid, M. P. 163-166 C.

2. A secondary phosphine, C13H25P, B. P. 123 C./8 mm., 4.5 parts.

Analysis calculated for C13H25P:

'C, 73.6%; H, 11.8%; P, 14.63% Found:

C, 73.83%; H, 11.94%; P, 14.40% 73.80% 11.90% 14.36%

This material is shown to be a secondary phosphine by treatment withmethyl iodide to give a white crystalline product, M. P. 78-80 C. whichwhen it is treated with base, releases an oil. A dry ether solution ofthe oil gives with carbon disulfide the deep red color characteristic oftertiary phosphines. The product thus appears to be a secondaryphosphine.

After washing the original solid product (194 6 parts) with benzene thesolid is extracted with hot acetone and hot alcohol. The insoluble partcomprises 14.7 parts of red phosphorus. From the acetone extract isisolated 5 parts of a crystalline compound, CieHzzPI, M. P. 168-170 C.,which is believed to be a phosphonium iodide.

Analysis calculated for C1eH32PI:

C, 50.52%; H, 8.38%; P, 8,12%; I, 33.30%

Found:

From the alcohol extract a crystalline compound, C12H25PI, M. P. 200-203C., of unknown structure is isolated.

Analysis calculated for C'12H25PI:

P, 9.50%; I, 39.00% Found:

Example VI A pressure reactor of the type used in the preceding examplesis charged with 20.6 parts (0.66 mole) of white phosphorus, 14.2 parts(0.1 mole) of methyl iodide, 84 parts (2 moles) of propylene, and 50parts of cyclohexane. This mixture is heated at 250 C. for 15 hoursunder 1,000 atmospheres hydrogen pressure. A total drop of 795atmospheres pressure occurs during the reaction. The product consists of43 parts of liquid and 52 parts of a brownish-black solid. The liquidportion is fractionally distilled and, in addition to 25 parts ofrecovered cyclohexane, the following products are isolated.

l. Monopropyl phosphine, boiling point 50.- 52 C., 3 parts.

2. Tripropyl phosphine, boiling point 186 C., 2 parts. The tripropylphosphine reacts with methyl iodide to form crystals ofmethyltripropylphosphonium iodide having a melting point of 200-202 C.It also reacts with carbon disulfide to give an addition product havinga melting point of 96-99 C. (with decomposition).

Analysis: Calculated for (C3H-z)sP.CS2:

P, 13.13% H, 8.9% C, 50.8% S. 27.10% Found:

P, 13.16% H, 9.71% 13.93% 9.95% 'C, 51.42% S, 26.19%

The solid reaction product is extracted with ethanol, leaving 14.5 partsof insoluble material. The ethanol solution is concentrated and ethylacetate is added to it, whereupon 10 parts of white crystals oftripropylphosphonium hydroiodide melting at 205-208 C. are obtained.These crystals are recrystallized from ethyl acetate and ethanol foranalysis.

Analysis: Calculated for (CaH'mP-HI:

C, 37.50% I. 44.10% Found:

In addition to the specific unsaturated hydrocarbons mentioned in theexamples, the process of this invention can be carried out with anyother hydrocarbon having at least one. oleiinic double bond. Specificexamples of other olefins, or alkenes, which are operable includeisobutylene and decene. Examples of other diolefins which can be usedinclude isoprene, dimethyl butadiene and the like. Also, othercycloolefins which are, operable include cyclopentene,l-methyl-l-cyclohexene, and 2,4-dimethyl4-cyclohexene. Unsaturatedhydrocarbons of the above types having 2 to carbon atoms and 1 to, 2ethylenic bonds are especially preferred.

A wide variety of halogens and halogen compounds can be used ascatalysts for the preparation of phosphines by the process of thisinvention. The following compounds are especially valuable for thispurpose: halogens such as, for example, iodine; alkyl halides, e. g.,methyl iodide and ethyl bromide; cycloalkyl halides, e. g. cyclohexyliodide; and inorganic halides, e. g., phosphorus tribromide. Thesehalogen and halide catalysts are used in proportions ranging from 10 to30 mole per cent of the phosphorus, employed. Especially good resultsare obtained when the catalyst amounts to from to mole per cent based onphosphorus.

The solvent, which is optional in the process of this invention, can bea hydrocarbon or an ether. Examples of suitable solvents includehydrocarbons such as cyclohexane and toluene; and others such as diethylether, dibutyl ether and dioxane.

The products of this invention are particularly useful as chemicalintermediates for the formation of a wide variety of other organophosphorus compounds such as phosphinic and phosphonic acids, etc. Theorganic phosphines and phosphonium halides are also useful asinsecticides, fungicides, antioxidants and lubricating oil additives.

The process of this invention is especially useful since it provides amethod for the preparation of organic phosphines and phosphonium halidesfrom relatively low cost starting materials.

As many apparently widely difierent embodiments of this invention may bemade Without departing from the spirit and scope thereof, it is to beunderstood that this invention is not limited to the specificembodiments thereof except as defined in the appended claims.

I claim:

1. A process which comprises heating a mixture of a hydrocarbon havingone to two ethylenic double bonds, white phosphorus and hydrogen at atemperature of 250 to 400 C.. and under a pressure of 700 to 3000atmospheres.

2. A process which comprises heating a mix- I ture of a hydrocarbonhaving one to two ethylenic double bonds, white phosphorus and hydrogenat 3. A process which comprises heating in an 8 inert solvent a mixtureof a hydrocarbon having one to two ethylenic double bonds, whitephosphorus and hydrogen at a temperature of 300 C. to 400 C., and undera pressure of 700 to 30.00 atmospheres.

4. A process which comprises heating a mixture of ethylene, whitephosphorus and hydrogen at a temperature of 250 C. to 400 C., and undera pressure of 700 to 3000 atmospheres.

5. A process which comprises heating a mixture of butadiene, whitephosphorus and hydrogen at a temperature of 250 C. to 400 C., and undera pressure of 700 to. 3000 atmospheres.

6. A process which comprises heating a mixture of cyclohexene, whitephosphorus and hydrogen at a temperature of 250 C. to 400 C., and undera pressure of 700 to 3000 atmospheres.

7. A process which comprises heating a mixture of propylene, Whitephosphorus and hydrogen at a temperature of 250 C. to 400 C., and undera pressure of 700 to 3000 atmospheres.

8. The chemical compound, tricyclohexylphosphine.

9. A process which comprises heating a mixture of a hydrocarbon havingone ethylenic double bond, white phosphorus and hydrogen at atemperature of 300 C. to 400 C. and under a pressure of 700. to 3000atmospheres.

10. A process which comprises heating a mixture of a hydrocarbon havingtwo ethylenic double bonds, white phosphorus and hydrogen at atemperature of 300 C. to 400 C., and under a pressure of 700 to 3000atmospheres.

l1. Tetracyclohexylphosphonium iodide.

12. lricyclohexylphosphine hydroiodide.

13. TricycloheXylmethylphosphonium iodide.

14. A process which comprises heating a mixture of a hydrocarbon havingone to two ethylenic double bonds, white phosphorus and hydrogen at atemperature of 250 C. to 400 C., and under a pressure of 700 to 3,000atmospheres in the presence of methyl iodide.

15. A process which comprises heating a mixture of cyclohexene, whitephosphorus, and hydrogen at a temperature of 250 C. to 400 C., and undera pressure of 700 to 3000 atmospheres in the presence of cyclohexyliodide.

16. A compound selected from the class consisting oftricyclohexylphosphine, tetracyclohexylphosphonium iodide,tricyclohexylphosphine hydroiodide and tricyclohexyimethylphosphoniurniodide.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,150,840 Dreyfus June 6, 1939 2,584,112 Brown Feb. 5. 1952OTHER REFERENCES Deutsche Chemische Gesellschaft-Berichte, 6, 1873, pp.296 and 297.

Mellor, Comprehensive Treatise on Inorganic and Theoretical Chemistry,vol. 8, p. 806.

1. A PROCESS WHICH COMPRISES HEATING A MIXTURE OF A HYDROCARBON HAVINGONE TO TWO ETHYLENIC DOUBLE BONDS, WHITE PHOSPHORUS AND HYDROGEN AT ATEMPERATURE OF 250* C. TO 400* C. AND UNDER A PRESSURE OF 700 TO 3000ATMOSPHERES.
 16. A COMPOUND SELECTED FROM THE CLASS CONSISTING OFTRICYCLOHEXYLPHOSPHINE, TETRACYCLOHEXLYPHOSPHONIUM IODIDE,TRICYCLOHEXYLPHOSPHINE HYDROIODIDE AND TRICYCLOHEXYLMETHYLPHOSPHONIUMIODIDE.